Ariel was the second book of Sylvia Plath's poetry to be published. It was originally published in 1965, two years after her death by suicide. The poems in the 1965 edition of Ariel, with their free flowing images and characteristically menacing psychic landscapes, marked a dramatic turn from Plath's earlier Colossus poems. In a BBC interview, Plath cited Robert Lowell's book "Life Studies" as having had a profound influence over the poetry she was writing in this last phase of her writing career. In the same interview, Plath also cited the poet Anne Sexton as an important influence on her writing during this time since Sexton was also exploring some of the same dark, taboo, personal subject matter that Plath was exploring in her writing. In 2004 a new edition of Ariel was published which for the first time restored the selection and arrangement of the poems as Plath had left them; the 2004 edition also features a foreword by Plath and Hughes' daughter Frieda Hughes.

https://en.wikipedia.org/wiki/Ariel_(poetry_collection)